Because the OP found a black and blue stripe on his HiPo Metuchen Oct 65 kar, does that mean Tony Gregory's 289 HiPo 4th edition book is wrong on page 164 when is says the drive shaft has 2 purple stripes and 1 pink stripe?
Possibly no. We see markings change during production years so what may have been correct for a May car might be completely different for a Dec car. I went to cataloging them by car production month to track and compare them - especially the 65-66 Hipo examples
Also few original examples remain after all these years and a fair number of owners have IMHO simply made up markings as a result of pressure they put on themselves to have something there.
When asked a number have simply responded no they aren't original but who will ever know
Note: I found the number 307 in pink on my rear yoke which shares the same part number C3AA-4868-G and my kar is also a Metuchen Oct 23 1965 K-code fastback.
May be a mark that the shop that replaced the tube and balanced it added. Normally you will find color (for a number of purposes) sprays and or daubs